6.0 g of a certain compound x, known to be made of carbon, hydrogen and perhaps oxygen, and to have a molecular molar mass of 138 g/mol, is burned completely in excess oxygen, and the mass of the products carefully measured:
carbon dioxide - 13.39 g
water - 2.35 g
use this information to find the molecular formula of x.

The compound X that have a molecular molar mass of 138 g/mol is

Given here,

Compound x - 6g

malar mass of x - 138g/mol

Carbon dioxide - 13.39 g

water - 2.35g

So,

The moles of Water will be 0.13 mol

The moles of Hydrogen will be 0.26

Mass of hydrogen = 0.26 g

The moles of carbon dioxide will be 0.304

The moles of carbon will be 0.304

Mass of Carbon = 3.65 g

Mass of  Oxygen = Total mass of the compound - (mass of C + mass of H)

= 6.0 g - ( 3.65 + 0.262 ) g

= 2.09 g

Moles of oxygen = 0.131

Since Oxygen has least moles,

To find the molar ratio of constituent atom, divide moles of atom from oxygen.

convert 2.3 into whole number

Hence formula will be

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The molecular formula of X is given as

Explanation:

mass O = Total mass of the compound - (mass of C + mass of H)

=6.0 g - ( 3.65 + 0.262 ) g

=2.09 g

Least moles is for O that is 0.131mol and dividing all by the least we get

Since 2.3 is a fraction it has to be converted to a whole number so we multiply all the answers by 3

So the empirical formula is

Empirical formula mass

Molecular formula =n × empirical formula

Compound X  =  is the Answer

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